Thermal distortion analysis of an antenna-support truss in geosynchronous orbit

The effects of the geosynchronous thermal environment on the surface accuracy of a tetrahedral-truss support structure for a high-frequency microwave antenna concept for Earth-science monitoring have been studied. The thermal environment and the slow rotation of the spacecraft relative to the Sun result in long exposure to both heating and cooling conditions and, consequently, in severe temperature extremes. Resulting transient temperatures ranged from 150 to -180 degree C and were strongly influenced by the shadow cast by the reflector surface. The use of truss element surface coatings achieved mixed success in alleviating thermal problems. Multilayer insulation of a Sun shield worked best in reducing surface distortions, but the distortions still exceeded the required surface accuracy. Surface accuracy requirements could only be met by customization of surface coatings and element expansion characteristics.